... is an epithet for James I of England and VI of Scotland, commonly attributed to Henry IV of France. In fact, no one is very sure who coined it.
The primary source is a book entitled The Court and Character of King James I (1651), which says that "A very wise man was wont to say that he believed him the wisest fool in Christendom, meaning him wise in small things, but a fool in weighty affairs." This book is generally attributed to Sir Anthony Weldon, a former courtier of James I who had been dismissed after publishing a book that was critical of Scotland (and thus held a grudge). Wikipedia says that "this attribution has been challenged" – but doesn't say who by.
Wikipedia does cite a 2003 book which suggested that the label may have been coined by Weldon.
I have also seen Maximilien de Béthune, Duc de Sully – Henry IV's superintendent of finances – cited as a possible originator of the epithet.
© Haydn Thompson 2017